When our soul begins to lose its appetite for earthly beauties, a spirit of listlessness is apt to steal into it. This prevents us from taking pleasure in study and teaching, and from feeling any strong desire for the blessings prepared for us in the life to come; it also leads us to disparage this transient life excessively, as not possessing anything of value. It even depreciates spiritual knowledge itself, either on the grounds that many others have already acquired it or because it cannot teach us anything perfect. To avoid this passion, which dejects and enervates us, we must confine the mind within very narrow limits, devoting ourselves solely to the remembrance of God. Only in this way will the intellect be able to regain its original fervor and escape this senseless dissipation.

When we have blocked all its outlets by means of the remembrance of God, the intellect requires of us imperatively some task which will satisfy its need for activity. For the complete fulfillment of its purpose we should give it nothing but the prayer ‘Lord Jesus’, ‘No one’, it is written, ‘can say “Lord Jesus” except in the Holy Spirit’ (1 Cor. 12:3). Let the intellect continually concentrate on these words within its inner shrine with such intensity that it is not turned aside to any mental images. Those who meditate unceasingly upon this glorious and holy name in the depths of their heart can sometimes see the light of their own intellect. For when the mind is closely concentrated upon this name, then we grow fully conscious that the name is burning up all the filth which covers the surface of the soul; for it is written: ‘Our God is a consuming fire’ (Deut. 4:24). Then the Lord awakens in the soul a great love for His glory; for when the intellect with fervor of heart maintains persistently its remembrance of the precious name, then that name implants in us a constant love for its goodness, since there is nothing now that stands in the way. This is the pearl of great price which a man can acquire by selling all that he has, and so experience the inexpressible joy of making it his own (cf. Matt. 13; 46). 

St. Diadochos of Photiki